Certain known types of locking rings for electric utility kilowatt-hour meters comprise split rings having radially outward extensions at the free ends. These ends are clamped together with a tangential screw to lock the meter tightly down on the meter base. A known type of steel cover completely encloses and protects the locked ring end extensions. The cover has an open end which receives the ring end extensions and abuts the meter when in fully engaged position. The cover has a pair of inner partitions disposed parallel to and laterally outward on either side of the ring end extensions. Aligned tangential apertures are provided in the outer ends of the ring end extensions, in the partitions, and in the right side of the cover, for receiving a known form of hollow cylinder barrel lock having an annular head which extends laterally outward of the cover for a short distance and which locks the cover in place. The annular head of the barrel lock has a transverse diametral hole for insertion of a lead seal wire. The inner end of the barrel lock has a pair of opposed transverse ball detents which extend laterally outward beyond the inward partition and prevents withdrawal of the barrel lock. These detents are releasable by means of a known form of cylindrical key which is inserted into the hollow end of the barrel lock and is operated by a cammed handle provided at the outer end. This key has a longitudinally split insert element of small diameter which is insertable in the hollow of the barrel lock and is adapted for spreading the outer ends of the insert element to release the ball detent locking mechanism in the barrel lock.
Kilowatt-hour meters of electric utility power companies are frequently installed in exposed locations where they are subject to tampering. Attempts have been made, for example, to drill into the barrel lock central aperture. This action is usually not productive but often leaves a broken drill in the barrel lock aperture which prevents the key from being used to remove the barrel lock. Also, due to exposure to weather and other conditions, the inner mechanism of the barrel lock, after long periods of time, sometimes becomes so corroded that the key is inoperative to release the ball detents, and the barrel lock then cannot be removed by means of the key.